1. Field of the Invention
The field of the invention relates to syringe safety systems and in particular to syringe shield systems for protecting against needle sticks.
2. Brief Description of the Related Art
Syringes are well known medical devices for administering medicaments, drugs and vaccines to patients. Prefilled syringes are generally considered as those which are filled with a selected dosage of medicament, drug or vaccine by a pharmaceutical manufacturer for distribution to the end user. They are generally comprised of a glass barrel which contains the medicament, drug or vaccine, and a stopper slidably mounted within the barrel. The distal end of the barrel includes a needle cannula or the like affixed thereto or a connector for a needle cannula assembly such as a Luer connector. The proximal end of the syringe includes an integral flange and is open to allow the insertion of a stopper and a plunger assembly. The plunger and stopper assembly allows the user to apply manual force to the plunger, causing the medicament, drug or vaccine to be delivered through the needle cannula or other piercing element. The healthcare worker or patient grips the flange and applies pressure to the plunger generally with the thumb.
The use of a sharp-pointed piercing element entails several types of risks. As long as the syringe is not in use ifs content is protected by a sterility cover that also prevents accidental an needle prick. Once the needle is exposed there are risks of accidental needle prick after use when the needle is contaminated, of accidental needle prick in case the syringe was not properly disposed of, and a risk of accidental or deliberate re-use. To avoid such accidents, many prior art hypodermic syringes have included different safety shields. Some of these considered telescopic shielding over the syringe barrel, others consider unique glass barrels. Telescoped shields can be moved between a retracted position, where the needle is exposed for use, to an extended position where the needle is surrounded by the shield.
U.S. Pat. No. 6,159,184 describes such a telescopic shield where the user is expected to identify the end of drug delivery and then use his second hand to manually push the shield until it locks to the holder. Sampson et al demonstrate this approach in a number of earlier patents such as U.S. Pat. No. 6,004,296, U.S. Pat. No. 4,425,120 and U.S. Pat. No. 4,573,976 also planned for a prefilled syringe.
U.S. Pat. No. 4,923,447 by Morgan discloses a shield system for hypodermic syringes which is spring-actuated. The release of the spring and triggering of the safety feature depends on the users action.
It is ordinarily desirable to lock the needle shields in the protected positions, and a number of prior art designs provide for such locking. Some systems, such as those disclosed in U.S. Pat. Nos. 5,201,708, 5,242,240 and U.S. Pat. No. 5,318,538 by Martin, are designed to allow the shields to be retracted from their locked, extended positions.
Another approach is demonstrated in U.S. Pat. No. 6,613,022 by Doyle where the user unsnaps a preloaded spring by moving the driver close to it's end of delivery position. The user is also expected to release his gripping fingers to allow the telescoping shield, which is external to the holder in that case, to slide forward and lock.
The safety shield could be activated by different means. In U.S. Pat. No. 6,613,022, the driver has to reach a certain position relative to the holder; in patent application 20030050607 by Gagnieux the user is expected to apply an increased pressure over the driver to do the same.